The present invention relates to novel polymers containing functional groups. More particularly the present invention relates to homopolymers and block copolymers containing reactive functionality or precursors convertible to such reactive functionalities. The present compositions are elastomeric or rigid thermoplastics depending on the components thereof and may be used as molding polymers and modifiers for rigid thermoplastics or reacted by means of the included functionality. Beneficially the polymers may be prepared to contain only a minimum quantity of functionalizing groups distributed at specific sites within the polymer.